The neuropeptide oxytocin (OT) has been thought of as an affiliation hormone because it plays a key role in the formation of adult pair- bonds and initiation of maternal behavior in non-human mammals. Investigators have speculated that oxytocin makes positive social contact more rewarding or increases social sensitivity. There is evidence that oxytocin regulation differs in those with specific psychiatric conditions (e.g., depression, obsessive-compulsive disorder) compared to controls. Little research has been conducted on this hormone with respect to its potential role in social behavior and psychological adjustment in humans. Basic research is needed on the characteristics of plasma OT in healthy adults. Both basal and pulsatile release of OT will be assessed in 40 healthy women of varying ethnicity, between the ages of 21 and 30. In the proposed study, we will measure levels of plasma OT to examine: (a) basal levels and their degree of stability over time (b) whether a positive emotional state elicits pulsatile release of OT (c) whether a negative emotional state inhibits pulsatile release of OT (d) whether the pattern of oxytocin release differs based on the individual's emotional and attachment- relevant personality traits. Finally, we will assess plasma prolactin levels to see if they are correlated with the occurrence of oxytocin pulses. Healthy participants will be recruited through flyers at local universities. Procedures will be conducted at the General Clinical Research Center at UCSF. Using indwelling catheter, blood draws at 5 ml each will occur every 5 minutes for 110 minutes. There will be a baseline period, positive emotion induction, interim period, and negative emotion induction. Emotion inductions will be accomplished through the standard Relived Emotions Task. Participants will also complete standard questionnaires on perceptions of childhood relationship with parents, emotional traits, personality, and psychological adjustment. Data will be analyzed using computer programs for hormone pulse detection.